Visual Torque Indicator for Threaded Joints
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Solution Overview
Problem
Threaded joints in machinery, such as fluid conduit joints in gas turbine engines, often fail to indicate proper torqueing, leading to potential leaks and safety issues, especially during field repairs by less experienced personnel.
Innovation Solution
Incorporating a visual torque indicator with strain-responsive materials, like piezochromic pigments, that change color in response to applied strain, allowing for visual inspection to confirm proper torqueing and detect over-torqueing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threaded joints are tightened in field conditions by less experienced personnel, then the joint may be tightened, but it is impossible to discern if the joint has been properly torqued
Solution Approach 1:
The patent applies piezochromic pigment to the coupling nut surface that changes color in response to applied strain. When the coupling nut is torqued to the proper torque, the pigment changes from one color state to another, providing immediate visual confirmation that the joint has been properly tightened. This resolves the contradiction by enabling field personnel to visually verify proper torque application without requiring specialized equipment or expertise.
2Difficulty of detecting and measuring
If no visual indicator is provided, then the joint structure remains simple, but the ability to detect proper torqueing is lost
Solution Approach 1:
The patent incorporates piezochromic pigment directly onto the coupling nut surface, creating a passive visual indicator that requires no additional power source, mechanism, or complex system. The pigment inherently changes color in response to the strain experienced during torquing, providing torque verification through a simple color change that can be seen with the naked eye.
Solution Approach 2:
The coupling nut itself serves as the indicator by incorporating the piezochromic pigment into its structure. The nut's own deformation during torquing directly causes the color change, eliminating the need for separate indicator devices, sensors, or verification systems. The joint structure performs both its fastening function and its indication function simultaneously.
3Reliability
If strain-responsive material is added to the coupling nut, then visual torque indication is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent describes applying piezochromic pigment to the coupling nut surface, which can be done through conventional coating methods. The pigment is applied to specific areas of the coupling nut where strain will be concentrated, allowing for precise torque indication while using standard manufacturing techniques.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The visual torque indicator provides a reliable method for ensuring secure threaded connections, reducing the risk of leaks and enabling quick verification of proper torque without the need for re-tightening, while also indicating potential damage or need for replacement.
Implementation Method 1
the torque indicator including a strain-responsive material configured to change visual appearance in response to the application of a strain thereto
Data Source
AI summary
A threaded element for a mechanical joint includes a body including threads and a visual torque indicator disposed on the body, the torque indicator including a strain-responsive material configured to change visual appearance in response to the application of a strain of a predetermined first magnitude thereto.